Orion Skywatcher 120 Questions

Amateur astronomy equipment, techniques, info, etc.

Orion Skywatcher 120 Questions

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Jon Isaa#1 / 9

Orion Skywatcher 120 Questions

Dear SAA knowledge base:

I recently picked up a Skywatcher 120 (F8.3) at a good price. Overall the scope works nicely but seems to have a good case of the shakes, trying to focus can be quite an experience, much like my old C8, adjust and wait for the vibration to die. Reminds me of why I like DOBs.... <g> But I would like to resolve this issue if possible.

This scope has the EQ-3 mount which is apparently a CG-4???

I do have the option of mounting the EQ head on an extremely sturdy tripod if that would help matters but my suspicion is that the head itself contributes significantly.

Anyway, I would appreciate suggestions on improving this situation and any pointers to websites that may address issues on improving these mounts.

Thanks for your time and thoughts.....

Jon Isaacs

Thu, 28 Oct 2004 23:42:42 GMT

Eric Fulle#2 / 9

Orion Skywatcher 120 Questions

Jon,

I have an original Vixen GP that I use for most things, and it is fine. But the maximum weight allowance is 16 lb. Unfortunately, they never stated the maximum angular moment allowed. This is likely the source of your problem as that telescope (5" f/8") is fairly large. Even on a GP mount, a 4" f/12 is basically at the limit of the mount.

The EQ-3 is essentially a clone of the old Vixen Super Polaris mount. The EQ-4, sometimes known as the EQ-5 is a clone of the Vixen Great Polaris mount.

I currently have an EQ-6 with the 6" f/8 refractor on it. The mount is balanced with 20 pounds of counterweight. Focussing is terrible at 300x... lots of jiggle. I might suggest that the 6" f/8 is at the limit of the EQ-6 in terms of angular moment.

The most prominent problem is the slop in the equatorial head. A quick rebuild solves much of this. I have seen a few pages about rebuilding the EQ-4, and GP mounts. There may be one out there for the EQ-6.

The next problem is the tripod... aluminum tripods are just not the thing to use. Switch to a heavy wood tripod or a permanent pier. The tripods that ship with the clone EQ-3 and EQ-4 are typically an aluminum extrusion (unless swapped out by thge distributor) which is lighter and cheaper than wood.

Good luck.

Eric.

Quote:

> Dear SAA knowledge base:

> I recently picked up a Skywatcher 120 (F8.3) at a good price. Overall the > scope works nicely but seems to have a good case of the shakes, trying to focus > can be quite an experience, much like my old C8, adjust and wait for the > vibration to die. Reminds me of why I like DOBs.... <g> But I would like to > resolve this issue if possible.

> This scope has the EQ-3 mount which is apparently a CG-4???

> I do have the option of mounting the EQ head on an extremely sturdy tripod if > that would help matters but my suspicion is that the head itself contributes > significantly.

> Anyway, I would appreciate suggestions on improving this situation and any > pointers to websites that may address issues on improving these mounts.

> Thanks for your time and thoughts.....

> Jon Isaacs

Fri, 29 Oct 2004 08:22:22 GMT

Rich McMah#3 / 9

Orion Skywatcher 120 Questions

John

Universal Astronomics should be able to solve your tripod problem. They provide a heavy duty wooden surveyors tripod and adapter.

Anderson Instruments also sells surveyors tripods but you will need to go to Universal Astronomics for the adapter.. Im using the wooden surveyors tripod to hold my cg-5 mount and 6" refractor. The wooden tripod made a huge improvment.

Rich

Quote:

>Dear SAA knowledge base:

>I recently picked up a Skywatcher 120 (F8.3) at a good price. Overall the >scope works nicely but seems to have a good case of the shakes, trying to focus >can be quite an experience, much like my old C8, adjust and wait for the >vibration to die. Reminds me of why I like DOBs.... <g> But I would like to >resolve this issue if possible.

>This scope has the EQ-3 mount which is apparently a CG-4???

>I do have the option of mounting the EQ head on an extremely sturdy tripod if >that would help matters but my suspicion is that the head itself contributes >significantly.

>Anyway, I would appreciate suggestions on improving this situation and any >pointers to websites that may address issues on improving these mounts.

>Thanks for your time and thoughts.....

>Jon Isaacs

Sat, 30 Oct 2004 12:48:43 GMT

William R. Matt#4 / 9

Orion Skywatcher 120 Questions

Quote:

>Dear SAA knowledge base:

>I recently picked up a Skywatcher 120 (F8.3) at a good price. Overall the >scope works nicely but seems to have a good case of the shakes, trying to focus >can be quite an experience, much like my old C8, adjust and wait for the >vibration to die. Reminds me of why I like DOBs.... <g>

Yes *we* all know how much you prefer the rumored stability of Dobs :^)

Quote:

>But I would like to >resolve this issue if possible.

Fix the problem. Replace the grease in the focuser with lithium grease and adjust the tension and fit until it is smooth and easy to turn. Most Synta scopes suffer from this same problem. They can also benefit from appropriate shims (teflon) as well.

Quote:

>This scope has the EQ-3 mount which is apparently a CG-4???

Probably not a good mount though I am sure there will be those that disagree. Adjust all axis until there is minimal backlash and no slop.

Quote:

>I do have the option of mounting the EQ head on an extremely sturdy tripod if >that would help matters but my suspicion is that the head itself contributes >significantly.

<sacrasm>

Be creative Jon. Dob mounts are soooo {*filter*}y superior why don't you use one of those ?

</sarcasm>

Seriously though .... piggyback it on the infamous Stable Dob we all hear so much about and if the {*filter*}y thing still shakes then it has to be the focuser

Quote:

>Anyway, I would appreciate suggestions on improving this situation and any >pointers to websites that may address issues on improving these mounts.

http://www.***.com/ http://www.***.com/

come join us on the "dark side" Jon .... you'll be glad you did :^)

See the appropriate page for upgrading the CG-5. Almost everthing there will work for that as well.

Bill

Sun, 31 Oct 2004 01:39:22 GMT

Jon Isaa#5 / 9

Orion Skywatcher 120 Questions

Quote:

>>But I would like to >>resolve this issue if possible. >Fix the problem. Replace the grease in the focuser with lithium grease and >adjust the tension and fit until it is smooth and easy to turn. Most >Synta scopes suffer from this same problem. They can also benefit from >appropriate shims (teflon) as well.

This is the sort of information I was looking for. The focuser is quite tight and this does seem to be part of the problem.

Quote:

>>This scope has the EQ-3 mount which is apparently a CG-4???

>Probably not a good mount though I am sure there will be those that >disagree. Adjust all axis until there is minimal backlash and no slop.

Sounds like a plan, I will give that a try.

Quote:

>>I do have the option of mounting the EQ head on an extremely sturdy tripod >if >>that would help matters but my suspicion is that the head itself contributes >>significantly.

><sacrasm>

Actually this is not sarcastic at all. Rather a friend gave me a tripod which apparently was originally meant to be used with a 35 mm Panavision type moving picture camera. It is very nicely made, very sturdy, it handles my 235 lbs jumping on it very nicely.

Mounting the EQ-3 head on this tripod is an option if it would help.

Quote:

>Seriously though .... piggyback it on the infamous Stable Dob we all >hear so much about and if the {*filter*}y thing still shakes then it has to >be the focuser

Actually I am interested in trying to improve this mount so that the scope can perform as it should. There is no doubt that a DOB mount is more stable but that is not the issue here, rather I would like to make the necessary improvements to this scope and mount so that I can enjoy advantages that it offers.

Quote:

>come join us on the "dark side" Jon .... you'll be glad you did :^)

>See the appropriate page for upgrading the CG-5. Almost everthing there >will work for that as well.

>Bill

Well, I am not selling anything but I do hope to get a feel for what a medium aperture, medium focal length achromat can do.

Thanks for your pointers and I will work on the focuser and mount ASAP.

jon isaacs

jon isaacs

Sun, 31 Oct 2004 05:36:13 GMT

Carl Pretoriu#6 / 9

Orion Skywatcher 120 Questions

Dear Jon I had the same experience with my 120. My question is would you want a GEM mount anyway? Ok, if you want to do atrophotos, but for a visual astronomer, a GEM is literally a pain in the back. If you look at the mechanics of the EQ3, you will see that the two axes of rotation are stabilised by about 4mm of metal contact on the worm to gear surfaces and the gears themselves (on mine anyway) must have been lathed by a novice - I measured 5 mil play between the gear and the shafts. No way that is ever going to be stable. Adding a Heargraves strut (see S&T of Sept.2001) and filling the tripod legs does help a lot. HOWEVER for the ultimate solution I threw away the EQ3 (actually I converted the tripod into a coffe cup and snack holder) and commisioned a machine shop to build a copy of the LightSpeed telescope Wagon mount, on a solid oak/carbon fibre pier mount. (I would have bought one, but since I am from South Africa and having toilet paper for currency it would have cost me 2 months salary after converion to US$1600). If you are from US, check out that mount at http://home.att.net/~Riddel.LightSpeed/wagon.htm. My buddies drool over the mount and it is the most stable thing I have ever seen (as in zero vibration = zero dampening time). A more affordable option, without the drives will be Nisur systems Taurus mount and their P3 pier mount for total $400). see http://nisursystems.com/index.html. Happy gazing Carlos

Mon, 01 Nov 2004 06:59:37 GMT

Jon Isaa#7 / 9

Orion Skywatcher 120 Questions

Quote:

>I had the same experience with my 120. My question is would you want a GEM >mount anyway? Ok, if you want to do atrophotos, but for a visual astronomer, >a GEM is literally a pain in the back.

One of the reasons I bought this scope was that it had a GEM. Every other scope I own is on some sort of an Alt-AZ mount and I figured it was time to see what I was missing. I had already done the fork thing so I thought it was time to do the GEM thing.

Well, so far my impression is that it is better than the Fork thing.

But I am sticking with this EQ, I already got the solid Alt-AZ thing under control.

<g>

jon isaacs

Mon, 01 Nov 2004 10:14:54 GMT

#8 / 9

Orion Skywatcher 120 Questions

Fri, 19 Jun 1992 00:00:00 GMT

Carl Pretoriu#9 / 9

Orion Skywatcher 120 Questions

Quote:

> One of the reasons I bought this scope was that it had a GEM. Every other > scope I own is on some sort of an Alt-AZ mount and I figured it was time to see > what I was missing. I had already done the fork thing so I thought it was time > to do the GEM thing.

> Well, so far my impression is that it is better than the Fork thing.

Point taken Jon, you like a GEM and nothing wrong with it. However I would like to make a case for a better GEM mount. Unless you are handy with a lathe and willing to rebuild your EQ3, you will always have a second class mount. Astronomy boys site has a nice discussion on how to improve the CG5 mount, and will translate directly to the EQ3 (http://www.astronomyboy.com/cg5/index.html). Coincidentally I took a long lunch today and visited my local Cats (local optics shops that stock Synta and Orion) and saw their new EQ-6 mount. Now that is a well-built piece of equipment, with a sturdy tripod reminiscent of a Meade. I am not sure whether Orion stocks that one yet. I do believe in wooden tripod legs, not just because of their dampening properties, but also their beauty. I would recommend a good Nisur pier mount (wooden legs, acrylic central pier). Perhaps the EQ-6 head on a Nisur pier mount? Now that will be a groovy combination. Regards Carlos